Flat plate heat exchangers are well known, and generally include a stacked plurality of generally flat, metal, heat exchange plates. The plates are supported in a generally parallel, vertical orientation between a base plate and a pressure plate, by means of a lower elongate carrying member, and an upper elongate guide member. The plates have generally U-shaped openings formed at their upper and lower outer edges, through which the elongate members extend, in a generally horizontal direction, so as to support the plates therebetween. It will be appreciated that the openings are shaped so as to enable mounting thereof between the elongate members, and such that they do not become dislodged therefrom, during assembly of the stack or during disassembly thereof.
A further consideration in securing a stack of heat exchanging plates in a flat plate heat exchanger is that the stack should ideally be fixated to a support structure so that no movement at all is possible, either between the plates, or between the plates and the support structure. This is due to the fact that any such movement can cause undesirable forces to be applied to liquid conduits extending in contact therewith, through the heat exchanger, thereby damaging them and, possibly causing mechanical failure thereof.
There exist in the art various solutions for ensuring secure fastening of the plates to the guide member, once they have been mounted in engagement therewith.
Among known attempts to solve the above problem is that described in U.S. Pat. No. 4,804,040 to Berqvist et al. Berqvist et al describe a plate heat exchanger, seen in FIG. 1A, having a plurality of heat exchange plates (i), which are arranged between a base plate (ii) and a pressure plate (iii), and which are supported by a lower carrying bar (iv). The lower carrying bar (iv), and an upper guide bar (v) extend through open-form recesses (not shown) in the respective lower and upper portions (vi) and (vii), respectively, of the plates (i).
At least the upper edge of each heat exchange plate (i) is provided with at least one transverse lug which is coplanar with the remainder of the plate, and which extends transversely into the recess so as to form a partial constriction thereof, thereby to assist in retaining the heat exchange plate (i) in engagement with the guide bar (v). The lug is described as being flexible enough to be bent aside, transversely to the plane of the plate, thereby to permit insertion of the guide bar (v) through the constriction and into the recess, and to spring back after the bar (v) has been inserted.
Among disadvantages inherent in the above-described heat exchange plates are the fact that it is required to maneuver each plate so as to force it onto the guide bar with a force that is sufficient to bend the lugs. This not only requires the use of a fair degree of force, but, in the event that too much force is exerted, the lugs can be bent too much so that they do not “spring back” into position. Furthermore, the nature of the connection of the plates is such that the support bar and guide bar are both absolutely necessary in order to immovably lock the plates in a stack arrangement.